Biscarbazole derivative and organic electroluminescent element using same

ABSTRACT

A biscarbazole derivative having a specific group, which is represented by formula (1); 
                         
and an organic electroluminescence device in which a plurality of organic thin-film layers including a light emitting layer are disposed between a cathode and an anode, and at least one of the organic thin-film layers include the biscarbazole derivative. The organic electroluminescence device exhibits high emission efficiency and has a long lifetime. In formula (1), each of A 1  and A 2  independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms; each of Y 1  to Y 16  independently represents C(R) or a nitrogen atom; each of R groups independently represents a hydrogen atom, etc.; and each of L 1  and L 2  independently represents a single bond, etc.; provided that at least one of A 1 , A 2  and R represents a substituted or unsubstituted fluoranthenyl group, etc.

TECHNICAL FIELD

The present invention relates to a biscarbazole derivative and anorganic electroluminescence device using the derivative, in particular,relates to an organic electroluminescence device having high emissionefficiency and a long lifetime, and a biscarbazole derivative forrealizing the device.

BACKGROUND ART

In recent years, many studies have been actively made on an organicthin-film light emitting device that emits light upon recombination ofelectrons injected from a cathode and holes injected from an anode in anorganic light emitting body interposed between both the electrodes. Thelight emitting device has been attracting attention because the deviceis thin and emits light with high luminance under a low driving voltage,and multi-color emission can be obtained by selecting light emittingmaterials.

When a voltage is applied to an organic electroluminescence device(hereinafter referred to as “organic EL device”), holes and electronsare injected into a light emitting layer from an anode and a cathode,respectively. Then, the holes and the electrons thus injected recombinein the light emitting layer to form excitons. At this time, singletexcitons and triplet excitons are produced at a ratio of 25%:75%according to the statistics theorem of electron spins. When the organicEL devices are classified by their light emission principles, theinternal quantum efficiency of a fluorescent organic EL device is saidto be at most 25% because the device uses light emission based on asinglet exciton. On the other hand, it has been known that as aphosphorescent organic EL device uses light emission based on a tripletexciton, its internal quantum efficiency reaches 100% when theintersystem crossing from a singlet exciton is efficiently performed.

The device design of organic EL devices has been optimized according tothe emission mechanisms of fluorescent devices and phosphorescentdevices. In particular, it has been known that a high-performancephosphorescent EL device is not obtained by merely applying thefluorescent device technology because of the difference in theiremission properties. The reason for this is generally considered to beas described below.

First, the phosphorescent emission is light emission from a tripletexciton and therefore a compound to be used in the light emitting layermust have a large energy gap. This is because that the energy gap of acertain compound (hereinafter also referred to as “singlet energy”) isgenerally larger than the triplet energy of the compound (energydifference between the lowest excited triplet state and the groundstate).

Therefore, to confine the triplet energy of a phosphorescent emittingdopant material efficiently in the device, first, a host material havinga larger triplet energy than the triplet energy of the phosphorescentemitting dopant material must be used in the light emitting layer.Further, an electron transporting layer and a hole transporting layermust be provided adjacent to the light emitting layer, and a compoundhaving a larger triplet energy than that of the phosphorescent emittingdopant material must be used in each of the electron transporting layerand the hole transporting layer. Therefore, according to the organic ELdevice design conventionally employed, a phosphorescent organic ELdevice using a compound having a larger energy gap than that of acompound used in fluorescent organic EL devices is resulted, thisincreasing the driving voltage of entire organic EL device.

In addition, a hydrocarbon compound having high oxidation resistance orhigh reduction resistance that has been useful in a fluorescent devicehas a small energy gap because of its wide distribution of π-electroncloud. Therefore, such a hydrocarbon compound is hardly selected in thephosphorescent organic EL device and an organic compound containing aheteroatom such as oxygen or nitrogen is selected instead. However, theorganic compound containing a heteroatom shortens the lifetime ofphosphorescent organic EL device as compared with that of fluorescentorganic EL device.

Further, the device performance is largely affected by the fact that theexciton relaxation rate of a triplet exciton of the phosphorescentemitting dopant material is extremely longer than that of a singletexciton. Since the relaxation of a singlet exciton which causes emissionis fast, the diffusion of the exciton into layers adjacent to the lightemitting layer (such as a hole transporting layer and an electrontransporting layer) hardly occurs and the efficient light emission isexpected. On the other hand, since the emission from a triplet excitonis a spin-forbidden process, and therefore, the relaxation causing theemission is slow, the exciton is apt to diffuse into the adjacentlayers, thereby causing the thermal energy deactivation of the exciton,although some specific phosphorescent emitting compounds lead todifferent results. Therefore, the control of the recombination zone ofelectrons and holes is more important, as compared with fluorescentorganic EL devices.

For the reasons described above, the development of a high-performancephosphorescent organic EL device needs the material selection and devicedesign which are different from those for the fluorescent organic ELdevices.

One of the most important problems to be solved in the organic thin-filmlight emitting device is the compatibility between high emissionefficiency and a low driving voltage. To obtain a high-efficiency lightemitting device, it has been known to form a light emitting layer bydoping a host material with a several percent of a dopant material(Patent Document 1). The host material is required to have a highcarrier mobility, a uniform film formability, etc. and the dopantmaterial is required to have a high fluorescent quantum yield, a uniformdispersibility, etc.

A fluorescent (singlet light emission) material has been generally usedas the dopant material. To improve the emission efficiency, the use of aphosphorescent (triplet light emission) material has been attempted, anda group of Princeton University has reported that the phosphorescentmaterial provides much higher emission efficiency than obtained by thefluorescent material (Non-Patent Document 1). Many techniques for usinga metal complex containing a central metal such as iridium, osmium,rhodium, palladium, and platinum as the phosphorescent dopant materialhave been disclosed (Patent Documents 2 to 4). As to the host materialto be combinedly used with the phosphorescent dopant material, thetechniques of using a carbazole derivative, an aromatic aminederivative, a quinolinol metal complex, etc. have been disclosed (PatentDocuments 2 to 6). However, a sufficient emission efficiency and a lowdriving voltage has not been obtained by none of the proposed materials.

A technique of using a biscarbazole derivative as a hole transportingmaterial of a fluorescent device has been disclosed (Patent Document 7).Some patent documents disclose a technique of using a biscarbazolederivative as a host material of phosphorescent device. For example,Patent Document 8 describes a biscarbazole derivative as a host materialto be combinedly used with a specific metal complex dopant. However, ahigh light emission is not obtained by the disclosed biscarbazolederivatives. Patent Document 9 describes the use of a biscarbazolederivative as a host material, in which a substituent for improving thecarrier transporting ability of the host material, such as anamino-substituted phenyl group, a naphthyl group, or a fluorenyl group,is introduced into the N-position of a carbazole structure. Although thedriving voltage of a light emitting device is reduced by the proposedbiscarbazole derivative, its effect on the lifetime is unclear.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP 2814435-   Patent Document 2: JP 2003-526876A-   Patent Document 3: JP 2003-515897A-   Patent Document 4: JP 2003-81988A-   Patent Document 5: JP 2003-133075A-   Patent Document 6: JP 2002-540572A-   Patent Document 7: JP 3139321-   Patent Document 8: JP 4357781-   Patent Document 9: JP 2008-135498A

Non-Patent Document

-   Non-Patent Document 1: Applied Physics Letters, 1999, vol. 75, No.    1, p. 4

SUMMARY OF INVENTION Problem to be Solved

The present invention has been made under such circumstances, and anobject of the present invention is to provide an organicelectroluminescence device having high emission efficiency and a longlifetime, and a biscarbazole derivative for realizing the device.

Solution to Problem

As a result of extensive studies, the inventors have found that theobject is achieved by a biscarbazole derivative having a specificsubstituent. The present invention is based on this finding.

Namely, the present invention provides the following biscarbazolederivatives, materials for organic electroluminescence devices, andorganic electroluminescence devices. The definition of “hydrogen”referred herein includes a deuterium.

1. A biscarbazole derivative represented by formula (1):

wherein:

each of A₁ and A₂ independently represents a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms;

each of Y₁ to Y₁₆ independently represents C(R) or a nitrogen atom, andeach of R groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton; and

each of L₁ and L₂ independently represents a single bond, a substitutedor unsubstituted, divalent aromatic hydrocarbon group having 6 to 30ring carbon atoms, or a substituted or unsubstituted, divalent aromaticheterocyclic group having 2 to 30 ring carbon atoms,

provided that:

at least one of A₁, A₂ and R represents a substituted or unsubstitutedfluoranthenyl group, a substituted or unsubstituted triphenylenyl group,a substituted or unsubstituted benzophenanthrenyl group, a substitutedor unsubstituted benzotriphenylenyl group, a substituted orunsubstituted dibenzotriphenylenyl group, a substituted or unsubstitutedchrysenyl group, a substituted or unsubstituted benzochrysenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted phenanthrenyl group, a substituted or unsubstitutedbinaphthyl group, a substituted or unsubstituted dibenzophenanthrenylgroup, a substituted or unsubstituted naphthotriphenylenyl group, asubstituted or unsubstituted benzofluorenyl group, or a naphthyl group;

when Y₁ to Y₁₆ all represent C(R) wherein R is a hydrogen atom, Y₆ andY₁₁ are bonded to each other via a single bond, each of L₁ and L₂represents a single bond, and A₁ represents a phenanthrenyl group, A₂represents a phenyl group, a biphenylyl group, or a naphthyl group; and

when Y₁ to Y₁₆ all represent C(R) wherein R is a hydrogen atom, Y₆ andY₁₁ are bonded to each other via a single bond, each of L₁ and L₂represents a single bond, and A₁ represents a naphthyl group, A₁ and A₂are different from each other;

2. The biscarbazole derivative according to item 1, wherein at least oneof A₁ and A₂ of formula (1) represents a substituted or unsubstitutedfluoranthenyl group, a substituted or unsubstituted triphenylenyl group,a substituted or unsubstituted benzophenanthrenyl group, a substitutedor unsubstituted benzotriphenylenyl group, a substituted orunsubstituted dibenzotriphenylenyl group, a substituted or unsubstitutedchrysenyl group, a substituted or unsubstituted benzochrysenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted phenanthrenyl group, a substituted or unsubstitutedbinaphthyl group, a substituted or unsubstituted dibenzophenanthrenylgroup, a substituted or unsubstituted naphthotriphenylenyl group, or asubstituted or unsubstituted benzofluorenyl group;

3. The biscarbazole derivative according to item 1 or 2, which isrepresented by formula (2):

wherein each of A₁, A₂, Y₁ to Y₁₆, L₁, and L₂ is as defined in formula(1);

4. The biscarbazole derivative according to item 1 or 2, which isrepresented by formula (3) or (4):

wherein each of A₁, A₂, Y₁ to Y₁₆, L₁, and L₂ is as defined in formula(1);

5. The biscarbazole derivative according to any one of items 1 to 4,wherein -L₁-A₁ and -L₂-A₂ are different from each other;

6. The biscarbazole derivative according to any one of items 1 to 5,wherein each of L₁ and L₂ represents a divalent linking group;

7. The biscarbazole derivative according to any one of items 1 to 6,wherein A₁ represents a substituted or unsubstituted fluoranthenylgroup, a substituted or unsubstituted triphenylenyl group, a substitutedor unsubstituted benzophenanthrenyl group, a substituted orunsubstituted benzotriphenylenyl group, a substituted or unsubstituteddibenzotriphenylenyl group, a substituted or unsubstituted chrysenylgroup, a substituted or unsubstituted benzochrysenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted phenanthrenyl group, a substituted or unsubstitutedbinaphthyl group, a substituted or unsubstituted dibenzophenanthrenylgroup, a substituted or unsubstituted naphthotriphenylenyl group, or asubstituted or unsubstituted benzofluorenyl group, and A₂ represents asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms;

8. A biscarbazole derivative represented by formula (1a):

wherein:

one of A_(1a) and A_(2a) represents a group represented by formula (a)and the other represents a substituted or unsubstituted fluoranthenylgroup, a substituted or unsubstituted benzophenanthrenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted phenanthrenyl group, a substituted or unsubstitutedbinaphthyl group, a substituted or unsubstituted dibenzophenanthrenylgroup, a substituted or unsubstituted naphthotriphenylenyl group, or asubstituted or unsubstituted benzofluorenyl group;

each of Y_(1a) to Y_(16a) independently represents C(R) or a nitrogenatom, and each of R groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton;

each of L_(1a) and L_(2a) independently represents a single bond, asubstituted or unsubstituted, divalent aromatic hydrocarbon group having6 to 30 ring carbon atoms, or a substituted or unsubstituted, divalentaromatic heterocyclic group having 2 to 30 ring carbon atoms:

wherein each of Y₂₁ and Y₂₅ independently represents C(R_(a)) or anitrogen atom, and each of R_(a) groups independently represents ahydrogen atom or a substituent;

9. A material for an organic electroluminescence device comprising thebiscarbazole derivative according to any one of items 1 to 8;

10. An organic electroluminescence device comprising a plurality oforganic thin-film layers between a cathode and an anode, wherein theorganic thin-film layers comprises a light emitting layer and at leastone layer of the organic thin-film layers comprises the biscarbazolederivative according to any one of items 1 to 9;

11. An organic electroluminescence device comprising a plurality oforganic thin-film layers between a cathode and an anode, wherein theorganic thin-film layers comprises a light emitting layer and at leastone layer of the organic thin-film layers comprises a biscarbazolederivative represented by formula (10):

wherein:

one of A_(1′) and A_(2′) represents a substituted or unsubstitutedfluorenyl group and the other represents a substituted or unsubstitutedaromatic hydrocarbon group having 6 to 30 ring carbon atoms;

each of Y_(1′) to Y_(16′) independently represents C(R′) or a nitrogenatom, and each of R′ groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton; and

each of L_(1′) and L_(2′) independently represents a single bond, asubstituted or unsubstituted, divalent aromatic hydrocarbon group having6 to 30 ring carbon atoms, or a substituted or unsubstituted, divalentaromatic heterocyclic group having 2 to 30 ring carbon atoms;

12. The organic electroluminescence device according to item 10 or 11,wherein the light emitting layer comprises the biscarbazole derivativeas a host material;

13. The organic electroluminescence device according to item 12, whereinthe light emitting layer comprises a phosphorescent material;

14. The organic electroluminescence device according to item 13, whereinthe light emitting layer comprises the host material and thephosphorescent material which is an ortho-metallated complex of a metalatom selected from iridium (Ir), osmium (Os), and platinum (Pt);

15. The organic electroluminescence device according to item 14, whereinthe device further comprises an electron injecting layer between thecathode and the light emitting layer, and the electron injecting layercomprises a nitrogen-containing ring derivative;

16. The organic electroluminescence device according to item 15, whereinthe device further comprises an electron transporting layer between thecathode and the light emitting layer, and the electron transportinglayer comprises the biscarbazole derivative;

17. The organic electroluminescence device according to item 16, whereinthe device further comprises a hole transporting layer between the anodeand the light emitting layer, and the hole transporting layer comprisesthe biscarbazole derivative;

18. The organic electroluminescence device according to item 17, whereinthe device further comprises a reducing dopant on an interface betweenthe cathode and the organic thin-film layer;

19. A lighting device comprising the organic electroluminescence deviceaccording to any one of items 10 to 18; and

20. A display device comprising the organic electroluminescence deviceaccording to any one of items 10 to 19.

Effects of Invention

The present invention provides the organic electroluminescence devicehaving high emission efficiency and a long lifetime, and thebiscarbazole derivative for realizing the device.

BRIEF DESCRIPTION OF DRAWINGS

The FIGURE is a schematic view illustrating the construction of anexample of the organic electroluminescence device (also referred to as“organic EL device”) according to the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

The present invention will be described below in detail.

Structure of Organic El Device

The device structure of the organic EL device is first described.

Typical examples of the device structure of organic EL device include:

(1) anode/light emitting layer/cathode;

(2) anode/hole injecting layer/light emitting layer/cathode;

(3) anode/light emitting layer/electron injecting/transportinglayer/cathode;

(4) anode/hole injecting layer/light emitting layer/electroninjecting/transporting layer/cathode;

(5) anode/organic semiconductor layer/light emitting layer/cathode;

(6) anode/organic semiconductor layer/electron blocking layer/lightemitting layer/cathode;

(7) anode/organic semiconductor layer/light emitting layer/adhesionimproving layer/cathode;

(8) anode/hole injecting/transporting layer/light emittinglayer/electron injecting/transporting layer/cathode;

(9) anode/insulating layer/light emitting layer/insulatinglayer/cathode;

(10) anode/inorganic semiconductor layer/insulating layer/light emittinglayer/insulating layer/cathode;

(11) anode/organic semiconductor layer/insulating layer/light emittinglayer/insulating layer/cathode;

(12) anode/insulating layer/hole injecting/transporting layer/lightemitting layer/insulating layer/cathode; and

(13) anode/insulating layer/hole injecting/transporting layer/lightemitting layer/electron injecting/transporting layer/cathode.

Of the above, the structure (8) is preferably used, although not limitedthereto.

A space layer may be provided between the light emitting layers toprevent excitons generated in a phosphorescent light emitting layer fromdiffusing into a fluorescent light emitting layer.

An example of the device structure of the organic EL device of theinvention is schematically shown in the FIGURE.

The organic EL device 1 includes a transparent substrate 2, an anode 3,a cathode 4, and an organic thin-film layer 10 disposed between theanode 3 and the cathode 4.

The organic thin-film layer 10 includes a phosphorescent light emittinglayer 5 including a phosphorescent host as a host material and aphosphorescent dopant as a phosphorescent material. A layer, such as ahole injecting/transporting layer 6, may be provided between thephosphorescent light emitting layer 5 and the anode 3 while a layer,such as an electron injecting/transporting layer 7, may be providedbetween the phosphorescent light emitting layer 5 and the cathode 4.

An electron blocking layer may be provided on the anode 3 side of thephosphorescent light emitting layer 5 while a hole blocking layer may beprovided on the cathode 4 side of the phosphorescent light emittinglayer 5.

With these blocking layers, electrons and holes can be confined in thephosphorescent light emitting layer 5, thereby enhancing the excitongeneration in the phosphorescent light emitting layer 5.

The organic EL device of the invention may be any of a single coloremitting device of fluorescent or phosphorescent type, a white-emittingdevice of fluorescent-phosphorescent hybrid type, an emitting device ofa simple type having a single emission unit, and an emitting device of atandem type having two or more emission units. The “emission unit”referred to herein is the smallest unit for emitting light by therecombination of injected holes and injected electrons, which comprisesone or more organic layers wherein at least one layer is a lightemitting layer. Representative layered structures of the emission unitare shown below.

(a) Hole transporting layer/light emitting layer(/electron transportinglayer);

(b) Hole transporting layer/first phosphorescent light emittinglayer/second phosphorescent light emitting layer(/electron transportinglayer);

(c) Hole transporting layer/phosphorescent light emitting layer/spacelayer/fluorescent light emitting layer(/electron transporting layer);

(d) Hole transporting layer/first phosphorescent light emittinglayer/second phosphorescent light emitting layer/space layer/fluorescentlight emitting layer(/electron transporting layer);

(e) Hole transporting layer/first phosphorescent light emittinglayer/space layer/second phosphorescent light emitting layer/spacelayer/fluorescent light emitting layer(/electron transporting layer);and

(f) Hole transporting layer/phosphorescent light emitting layer/spacelayer/first fluorescent light emitting layer/second fluorescent lightemitting layer(/electron transporting layer).

Representative device structure of the tandem-type organic EL device isshown below:

anode/first emission unit/intermediate layer/second emissionunit/cathode.

The layered structure of the first emission unit and the second emissionunit may be selected from those described above with respect to theemission unit.

Generally, the intermediate layer is also called an intermediateelectrode, an intermediate conductive layer, a charge generation layer,an electron withdrawing layer, a connecting layer, or an intermediateinsulating layer. The intermediate layer may be formed by knownmaterials so as to supply electrons to the first emission unit and holesto the second emission unit.

In the present invention, a host is referred to as a fluorescent hostwhen combinedly used with a fluorescent dopant and as a phosphorescenthost when combinedly used with a phosphorescent dopant. Therefore, thefluorescent host and the phosphorescent host are not distinguished fromeach other merely by the difference in their molecular structures.

Namely, in the present invention, the term “fluorescent host” means amaterial for constituting a fluorescent emitting layer containing afluorescent dopant and does not mean a material that can be utilizedonly as a host for a fluorescent material.

Similarly, the term “phosphorescent host” means a material forconstituting a phosphorescent emitting layer containing a phosphorescentdopant and does not mean a material that can be utilized only as a hostfor a phosphorescent material.

The term “hole injecting/transporting layer” as used herein refers to atleast one of a hole injecting layer and a hole transporting layer, andthe term “electron injecting/transporting layer” as used herein refersto at least one of an electron injecting layer and an electrontransporting layer.

Transparent Substrate

The organic EL device of the invention is formed on a light-transmissivesubstrate. The light-transmissive substrate serves as a support for theorganic EL device and preferably a flat substrate having a transmittanceof 50% or more to 400 to 700 nm visible light.

Examples of the substrate include a glass plate and a polymer plate.

The glass plate may include a plate made of soda-lime glass,barium-strontium-containing glass, lead glass, aluminosilicate glass,borosilicate glass, barium borosilicate glass, or quartz.

The polymer plate may include a plate made of polycarbonate, acryl,polyethylene terephthalate, polyether sulfide, or polysulfone.

Anode and Cathode

The anode of the organic EL device injects holes to the hole injectinglayer, the hole transporting layer or the light emitting layer, and ananode having a work function of 4.5 eV or more is effective.

Examples of the material for anode include indium tin oxide alloy (ITO),tin oxide (NESA), indium zinc oxide alloy, gold, silver, platinum, andcupper.

The anode is formed by making the electrode material into a thin film bya method, such as a vapor deposition method or a sputtering method.

When getting the light emitted from the light emitting layer through theanode as in the embodiment of the invention, the transmittance of anodeto visible light is preferably 10% or more. The sheet resistance ofanode is preferably several hundreds Ω/□ or less. The film thickness ofanode depends upon the kind of material and generally 10 nm to 1 μm,preferably 10 to 200 nm.

The cathode is formed preferably from a material having a small workfunction in view of injecting electrons to the electron injecting layer,the electron transporting layer or the light emitting layer.

Examples of the material for cathode include, but not limited to,indium, aluminum, magnesium, magnesium-indium alloy, magnesium-aluminumalloy, aluminum-lithium alloy, aluminum-scandium-lithium alloy, andmagnesium-silver alloy.

Like the anode, the cathode is formed by making the material into a thinfilm by a method, such as the vapor deposition method and the sputteringmethod. The emitted light may be taken through the cathode.

Light Emitting Layer

The light emitting layer of the organic EL device combines the followingfunctions:

(i) The injecting function: the function of allowing the injection ofholes from the anode or the hole injecting layer and allowing theinjection of electrons from the cathode or the electron injecting layerwhen an electric field is applied;

(ii) The transporting function: the function of transporting injectedcharges (i.e., electrons and holes) by the force of the electric field;and

(iii) The light emitting function: the function of providing the areafor recombination of electrons and holes and leading the recombinationto the emission of light.

The light emitting layer may be different in its easiness of holeinjection and its easiness of electron injection, and also in the holetransporting ability and the electron transporting ability each beingexpressed by mobility.

The light emitting layer is formed, for example, by a known method, suchas a vapor deposition method, a spin coating method, and LB method.

The light emitting layer is preferably a molecular deposit film.

The molecular deposit film is a thin film formed by depositing avaporized material or a film formed by solidifying a material in thestate of solution or liquid. The molecular deposit film can bedistinguished from a thin film formed by LB method (molecular build-upfilm) by the differences in the assembly structures and higher orderstructures and the functional difference due to the structuraldifferences.

The light emitting layer can be formed also by making a solution of abinder, such as resin, and the material for the light emitting layer ina solvent into a thin film by a method such as spin coating.

The organic EL device of the invention comprises an organic thin filmlayer. The organic thin film layer comprises one or more layers at leastone of which is a light emitting layer. At least one layer of theorganic thin film layer comprises at least one kind of phosphorescentmaterial and at least one kind of material for organicelectroluminescence devices of the invention to be described later.Preferably, at least one light emitting layer comprises the material fororganic electroluminescence devices of the invention and at least onekind of phosphorescent material.

Biscarbazole Derivative

The organic EL device of the present invention has a plurality oforganic thin-film layers including a light emitting layer between thecathode and the anode, and at least one layer of the organic thin-filmlayers comprises the biscarbazole derivative. In the present invention,the definition of “hydrogen” includes a heavy hydrogen. In addition, thebiscarbazole derivative of the present invention preferably has only twocarbazole structures in a molecule thereof.

The biscarbazole derivative of the present invention has, at a specificposition, a substituted or unsubstituted fluoranthenyl group, asubstituted or unsubstituted triphenylenyl group, a substituted orunsubstituted benzophenanthrenyl group, a substituted or unsubstitutedbenzotriphenylenyl group, a substituted or unsubstituteddibenzotriphenylenyl group, a substituted or unsubstituted chrysenylgroup, a substituted or unsubstituted benzochrysenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted benzofuranyl group, a substituted or unsubstituteddibenzofuranyl group, a substituted or unsubstituted benzothiophenylgroup, a substituted or unsubstituted dibenzothiophenyl group, asubstituted or unsubstituted phenanthrenyl group, a substituted orunsubstituted fluorenyl group, a substituted or unsubstituted binaphthylgroup, a substituted or unsubstituted benzonaphthofuranyl group, asubstituted or unsubstituted benzonaphthothiophenyl group, a substitutedor unsubstituted dibenzophenanthrenyl group, a substituted orunsubstituted naphthotriphenylenyl group, a substituted or unsubstitutedbenzofluoranthenyl group, a substituted or unsubstituted benzofluorenylgroup, or a substituted or unsubstituted phenyl group. Examples thereofinclude compounds represented by any of formulae (1) to (4), (1′), (1a),and (10).

wherein;

each of A₁ and A₂ independently represents a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms;

each of Y₁ to Y₁₆ independently represents C(R) or a nitrogen atom, andeach of R groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton; and

each of L₁ and L₂ independently represents a single bond, a substitutedor unsubstituted, divalent aromatic hydrocarbon group having 6 to 30ring carbon atoms, or a substituted or unsubstituted, divalent aromaticheterocyclic group having 2 to 30 ring carbon atoms,

provided that;

at least one of A₁, A₂ and R represents a substituted or unsubstitutedfluoranthenyl group, a substituted or unsubstituted triphenylenyl group,a substituted or unsubstituted benzophenanthrenyl group, a substitutedor unsubstituted benzotriphenylenyl group, a substituted orunsubstituted dibenzotriphenylenyl group, a substituted or unsubstitutedchrysenyl group, a substituted or unsubstituted benzochrysenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted phenanthrenyl group, a substituted or unsubstitutedbinaphthyl group, a substituted or unsubstituted dibenzophenanthrenylgroup, a substituted or unsubstituted naphthotriphenylenyl group, asubstituted or unsubstituted benzofluorenyl group, or a naphthyl group;

when Y₁ to Y₁₆ all represent C(R) wherein R is a hydrogen atom, Y₆ andY₁₁ are bonded to each other via a single bond, each of L₁ and L₂represents a single bond, and A₁ represents a phenanthrenyl group, A₂represents a phenyl group, a biphenylyl group, or a naphthyl group; and

when Y₁ to Y₁₆ all represent C(R) wherein R is a hydrogen atom, Y₆ andY₁₁ are bonded to each other via a single bond, each of L₁ and L₂represents a single bond, and A₁ represents a naphthyl group, A₁ and A₂are different from each other

In formulae (1) and (1′), at least one of Y₁ to Y₄ represents C(R), atleast one of Y₅ to Y₈ represents C(R), at least one of Y₉ to Y₁₂represents C(R), and at least one of Y₁₃ to Y₁₆ represent C(R).

In addition, at least one of Y₅ to Y₈ represents C(R) and at least oneof Y₉ to Y₁₂ represents C(R), wherein two R groups represent valenceswhich are bonded to each other.

The R groups in formulae (1) and (1′) may be the same or different.

In formula (1a), at least one of Y_(1a) to Y_(4a) represents C(R), atleast one of Y_(5a) to Y_(8a) represents C(R), at least one of Y_(9a) toY_(12a) represents C(R), and at least one of Y_(13a) to Y_(16a)represents C(R).

In addition, at least one of Y_(5a) to Y_(8a) represents C(R) and atleast one of Y_(9a) to Y_(12a) represents C(R), wherein two R groupsrepresent valences which are bonded to each other.

The R groups in formula (1a) may be the same or different.

In formula (10), at least one of Y_(1′) to Y_(4′) represents C(R′), atleast one of Y_(5′) to Y_(8′) represents C(R′), at least one of Y_(9′)to Y_(12′) represents C(R′), and at least one of Y_(13′) to Y_(16′)represents C(R′).

In addition, at least one of Y_(5′) to Y_(8′) represents C(R′) and atleast one of Y_(9′) to Y_(12′) represents C(R′), wherein two R′ groupsrepresent valences which are bonded to each other.

The R′ groups in formula (10) may be the same or different.

wherein each of A₁, A₂, Y₁ to Y₁₆, L₁, and L₂ in formulae (2) to (4) isas defined in formula (1).

wherein:

each of A₁ and A₂ independently represents a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms or a substituted or unsubstituted aromatic heterocyclic grouphaving 2 to 30 ring carbon atoms;

each of Y₁ to Y₁₆ independently represents C(R) or a nitrogen atom, andeach of R groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton; and

each of L₁ and L₂ independently represents a single bond, a substitutedor unsubstituted, divalent aromatic hydrocarbon group having 6 to 30ring carbon atoms, or a substituted or unsubstituted, divalent aromaticheterocyclic group having 2 to 30 ring carbon atoms,

provided that:

at least one of A₁, A₂ and R represents a substituted or unsubstitutedfluoranthenyl group, a substituted or unsubstituted triphenylenyl group,a substituted or unsubstituted benzophenanthrenyl group, a substitutedor unsubstituted benzotriphenylenyl group, a substituted orunsubstituted dibenzotriphenylenyl group, a substituted or unsubstitutedchrysenyl group, a substituted or unsubstituted benzochrysenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted benzofuranyl group, a substituted or unsubstituteddibenzofuranyl group, a substituted or unsubstituted benzothiophenylgroup, a substituted or unsubstituted dibenzothiophenyl group, asubstituted or unsubstituted phenanthrenyl group, a substituted orunsubstituted fluorenyl group, a substituted or unsubstituted binaphthylgroup, a substituted or unsubstituted benzonaphthofuranyl group, asubstituted or unsubstituted benzonaphthothiophenyl group, a substitutedor unsubstituted dibenzophenanthrenyl group, a substituted orunsubstituted naphthotriphenylenyl group, a substituted or unsubstitutedbenzofluorenyl group, or a substituted or unsubstituted phenyl group;

when Y₁ to Y₁₆ all represent C(R) wherein R is a hydrogen atom, Y₆ andY₁₁ are bonded to each other via a single bond, each of L₁ and L₂represents a single bond, and A₁ represents a phenanthrenyl group, A₂does not represent a phenanthrenyl group;

when Y₁ to Y₁₆ all represent C(R), Y₆ and Y₁₁ are bonded to each othervia a single bond, and each of L₁ and L₂ represents a single bond, eachof R groups does not represent a fluorenyl group; and

when A₁ represents a fluorenyl group, A₂ does not represent a phenylgroup, a naphthyl group, or a fluorenyl group.

wherein:

one of A_(1a) and A_(2a) represents a group represented by formula (a)and the other represents a substituted or unsubstituted fluoranthenylgroup, a substituted or unsubstituted benzophenanthrenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted phenanthrenyl group, a substituted or unsubstitutedbinaphthyl group, a substituted or unsubstituted dibenzophenanthrenylgroup, a substituted or unsubstituted naphthotriphenylenyl group, or asubstituted or unsubstituted benzofluorenyl group;

each of Y_(1a) to Y_(16a) independently represents C(R) or a nitrogenatom, and each of R groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton;

each of L_(1a) and L_(2a) independently represents a single bond, asubstituted or unsubstituted, divalent aromatic hydrocarbon group having6 to 30 ring carbon atoms, or a substituted or unsubstituted, divalentaromatic heterocyclic group having 2 to 30 ring carbon atoms:

wherein each of Y₂₁ and Y₂₅ independently represents C(R_(a)) or anitrogen atom, and each of R_(a) groups independently represents ahydrogen atom or a substituent.

The details of A_(1a), A_(2a), Y_(1a) to Y_(16a), L_(1a), L_(2a), andR_(a) in formulae (1a) and (a) are the same as those of A₁, A₂, Y₁ toY₁₆, L₁, L₂, and R in formula (1).

When one of A_(1a) and A_(2a) represents a group represented by formula(a) and the other represents a group including a large molecular weightfused ring, such as a triphenylenyl group and a chrysenyl group, thecompound represented by formula (1a) has an excessively large molecularweight, increasing the vapor deposition temperature and therefore likelyto increase the amount of thermally decomposed components. Therefore,when one of A_(1a) and A_(2a) represents a group represented by formula(a), the other preferably represents a substituted or unsubstitutedfluoranthenyl group or a substituted or unsubstituted phenanthrenylgroup.

wherein:

one of A_(1′) and A_(2′) represents a substituted or unsubstitutednaphthyl group or a substituted or unsubstituted fluorenyl group and theother represents a substituted or unsubstituted aromatic hydrocarbongroup having 6 to 30 ring carbon atoms;

each of Y_(1′) to Y_(16′) independently represents C(R′) or a nitrogenatom, and each of R′ groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton; and

each of L_(1′) and L_(2′) independently represents a single bond, asubstituted or unsubstituted, divalent aromatic hydrocarbon group having6 to 30 ring carbon atoms, or a substituted or unsubstituted, divalentaromatic heterocyclic group having 2 to 30 ring carbon atoms.

The details of A_(1′), A_(2′), L_(1′), L_(2′), Y_(1′) to Y_(16′), and R′in formula (10) are the same as those of A₁, A₂, L₁, L₂, Y₁ to Y₁₆, andR in formula (1).

In formulae (1) to (4) and (1′), at least one of A₁, A₂ and R preferablyrepresents a substituted or unsubstituted fluoranthenyl group, asubstituted or unsubstituted triphenylenyl group, a substituted orunsubstituted benzophenanthrenyl group, a substituted or unsubstitutedbenzotriphenylenyl group, a substituted or unsubstituteddibenzotriphenylenyl group, a substituted or unsubstituted chrysenylgroup, a substituted or unsubstituted benzochrysenyl group, asubstituted or unsubstituted picenyl group, a substituted orunsubstituted benzo[b]fluoranthenyl group, a substituted orunsubstituted benzofuranyl group, a substituted or unsubstituteddibenzofuranyl group, a substituted or unsubstituted benzothiophenylgroup, a substituted or unsubstituted dibenzothiophenyl group, asubstituted or unsubstituted phenanthrenyl group, a substituted orunsubstituted fluorenyl group, or a substituted or unsubstitutedbinaphthyl group, because these groups are moderately bulky. Morepreferably, at least one of A₁ and A₂ represents a substituted orunsubstituted fluoranthenyl group, a substituted or unsubstitutedtriphenylenyl group, a substituted or unsubstituted benzophenanthrenylgroup, a substituted or unsubstituted benzotriphenylenyl group, asubstituted or unsubstituted dibenzotriphenylenyl group, a substitutedor unsubstituted chrysenyl group, a substituted or unsubstitutedbenzochrysenyl group, a substituted or unsubstituted picenyl group, asubstituted or unsubstituted benzo[b]fluoranthenyl group, a substitutedor unsubstituted benzofuranyl group, a substituted or unsubstituteddibenzofuranyl group, a substituted or unsubstituted benzothiophenylgroup, a substituted or unsubstituted dibenzothiophenyl group, or asubstituted or unsubstituted binaphthyl group.

Also preferably, each of A₁ and A₂ in formulae (1) to (4) and (1′)independently represents a substituted or unsubstituted fluoranthenylgroup, a substituted or unsubstituted triphenylenyl group, a substitutedor unsubstituted benzotriphenylenyl group, a substituted orunsubstituted benzophenanthrenyl group, a substituted or unsubstituteddibenzofuranyl group, or a substituted or unsubstituteddibenzothiophenyl group.

In addition, -L₁-A₁ and -L₂-A₂ in formulae (1) to (4) and (1′) arepreferably different from each other.

The substituted or unsubstituted phenyl group for any of A₁, A₂ and R ispreferably a phenyl group substituted by an aromatic hydrocarbon grouphaving 10 to 30 ring carbon atoms and particularly preferably anaphthylphenyl group.

When at least one of A₁ and A₂ in formulae (1) to (4) and (1′)represents a group represented by formula (a), the biscarbazolederivative is particularly preferred as a host material to be used incombination with a green emitting dopant.

In formula (a), Y₂₁ and/or Y₂₅ preferably represents a nitrogen atom,and each of Y₂₂ and Y₂₄ more preferably represents C(R_(a)).

Specific examples of the substituent which A₁ and A₂ in formulae (1) to(4) and (1′) may have and the substituents represented by R and R_(a)include a fluorine atom; a cyano group; a substituted or unsubstituted,linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms; alinear, branched, or cyclic alkylene group having 1 to 20 carbon atoms;a linear, branched, or cyclic, divalent, unsaturated hydrocarbon grouphaving 1 to 20 carbon atoms; a substituted or unsubstituted, linear,branched, or cyclic alkoxy group having 1 to 20 carbon atoms; asubstituted or unsubstituted, linear, branched, or cyclic haloalkylgroup having 1 to 20 carbon atoms; a substituted or unsubstituted,linear, branched, or cyclic haloalkoxy group having 1 to 20 carbonatoms; a substituted or unsubstituted, linear, branched, or cyclicalkylsilyl group having 1 to 10 carbon atoms; a substituted orunsubstituted arylsilyl group having 6 to 30 carbon atoms; a substitutedor unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms; and a substituted or unsubstituted aromatic heterocyclic grouphaving 2 to 30 ring carbon atoms. In addition, a plurality ofsubstituents of any such kind may exist, and when the plurality ofsubstituents exist, the substituents may be the same or different fromeach other.

The R groups on adjacent ring carbon atoms may be bonded to each otherto form a ring structure together with the ring carbon atoms.

Examples of the linear, branched, or cyclic alkyl group having 1 to 20carbon atoms include a methyl group, an ethyl group, a propyl group, anisopropyl group, a n-butyl group, a s-butyl group, an isobutyl group, at-butyl group, a n-pentyl group, a n-hexyl group, a n-heptyl group, an-octyl group, a n-nonyl group, a n-decyl group, a n-undecyl group, an-dodecyl group, a n-tridecyl group, a n-tetradecyl group, an-pentadecyl group, a n-hexadecyl group, a n-heptadecyl group, an-octadecyl group, a neopentyl group, a 1-methylpentyl group, a2-methylpentyl group, a 1-pentylhexyl group, a 1-butylpentyl group, a1-heptyloctyl group, a 3-methylpentyl group, a cyclopentyl group, acyclohexyl group, a cyclooctyl group, a 3,5-tetramethylcyclohexyl group,a trifluoromethyl group, a 2,2,2-trifluoroethyl group, and a1,1,1,3,3,3-hexafluoro-2-propyl group.

Examples of the linear, branched, or cyclic alkylene group having 1 to20 carbon atoms include an ethylene group, a propylene group, and abutylene group.

Examples of the linear, branched, or cyclic, divalent unsaturatedhydrocarbon group having 1 to 20 carbon atoms include a1,3-butadiene-1,4-diyl group.

Examples of the linear, branched, or cyclic alkylsilyl group having 1 to10 carbon atoms include a trimethylsilyl group, a triethylsilyl group, atributylsilyl group, a dimethylethylsilyl group, adimethylisopropylsilyl group, a dimethylpropylsilyl group, adimethylbutylsilyl group, a dimethyl-t-butylsilyl group, and adiethylisopropylsilyl group.

Examples of the arylsilyl group having 6 to 30 carbon atoms include aphenyldimethylsilyl group, a diphenylmethylsilyl group, adiphenyl-t-butylsilyl group, and a triphenylsilyl group.

Examples of the halogen atom include a fluorine atom.

Examples of the aromatic heterocyclic group having 2 to 30 ring carbonatoms include non-fused aromatic heterocyclic and fused aromaticheterocyclic groups, more specifically, a pyrrolyl group, a pyrazinylgroup, a pyridinyl group, an indolyl group, an isoindolyl group, a furylgroup, a benzofuranyl group, an isobenzofuranyl group, a dibenzofuranylgroup, a dibenzothiophenyl group, a quinolyl group, an isoquinolylgroup, a quinoxalinyl group, a carbazolyl group, a phenanthridinylgroup, an acridinyl group, a phenanthrolinyl group, a thienyl group, andresidues of a pyridine ring, a pyrazine ring, a pyrimidine ring, apyridazine ring, a triazine ring, an indole ring, a quinoline ring, anacridine ring, a pyrrolidine ring, a dioxane ring, a piperidine ring, amorpholine ring, a piperazine ring, a carbazole ring, a furan ring, athiophene ring, an oxazole ring, an oxadiazole ring, a benzoxazole ring,a thiazole ring, a thiadiazole ring, a benzothiazole ring, a triazolering, an imidazole ring, a benzimidazole ring, a pyran ring, adibenzofuran ring, and a benzo[c]dibenzofuran ring.

Examples of the aromatic hydrocarbon group having 6 to 30 ring carbonatoms include non-fused aromatic hydrocarbon groups and fused aromatichydrocarbon groups, more specifically, a phenyl group, a naphthyl group,a phenanthryl group, a biphenyl group, a terphenyl group, a quaterphenylgroup, a fluoranthenyl group, a triphenylenyl group, a phenanthrenylgroup, a 9,9-dimethylfluorenyl group, a benzo[c]phenanthrenyl group, abenzo[a]triphenylenyl group, a naphtho[1,2-c]phenanthrenyl group, anaphtho[1,2-a]triphenylenyl group, a dibenzo[a,c]triphenylenyl group,and a benzo[b]fluoranthenyl group.

Examples of the divalent linking group represented by L₁ and L₂ informulae (1) to (4) and (1′) include a substituted or unsubstituted,divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms anda substituted or unsubstituted, divalent aromatic heterocyclic grouphaving 2 to 30 ring carbon atoms.

Examples of the divalent aromatic hydrocarbon group having 6 to 30 ringcarbon atoms include groups obtained by making the examples of thearomatic hydrocarbon group having 6 to 30 ring carbon atoms mentionedabove into divalent groups.

In addition, specific examples of the divalent aromatic heterocyclicgroup having 2 to 30 ring carbon atoms include groups obtained by makingthe examples of the aromatic heterocyclic group having 2 to 30 ringcarbon atoms mentioned above into divalent groups.

In each of formulae (1) to (4) and (1′), Y₁ to Y₁₆ all preferablyrepresent C(R).

In each of formulae (1) to (4) and (1′), the number of substituentsrepresented by R in Y₁ to Y₈ or in Y₉ to Y₁₆ is preferably 0 to 2, morepreferably 0 or 1.

Specific examples of the biscarbazole derivative of the presentinvention represented by any one of formulae (1) to (4), (1′), and (10)include the following compounds. In the following structural formulae, Drepresents a heavy hydrogen (deuterium).

The organic EL device of the invention contains the biscarbazolederivative of the invention preferably in the light emitting layer.

It is also preferred that the organic EL device of the inventioncomprises a hole transporting layer (hole injecting layer) and the holetransporting layer (hole injecting layer) comprises the biscarbazolederivative of the invention.

Phosphorescent Material

In the present invention, the phosphorescent material comprises a metalcomplex. The metal complex preferably comprises a metal atom selectedfrom Ir, Pt, Os, Au, Cu, Re, and Ru, and a ligand. In particular, aligand having an ortho metal bond is preferred.

In view of obtaining a high phosphorescent quantum yield and furtherimproving the external quantum efficiency of electroluminescence device,a metal complex comprising a metal selected from Ir, Os, and Pt ispreferred. A metal complex, such as iridium complex, osmium complex, andplatinum complex, is more preferred, with iridium complex and platinumcomplex being still more preferred, and an ortho metallated iridiumcomplex being most preferred.

Specific examples of the preferred metal complex are shown below.

In a preferred embodiment of the invention, at least one of thephosphorescent materials used in the light emitting layer emit lighthaving a maximum emission wavelength of preferably 450 nm or longer and750 nm or shorter. In another preferred embodiment, the maximum emissionwavelength is 450 nm or longer and 495 nm or shorter, 495 nm or longerand 590 nm or shorter, or 590 nm or longer and 750 nm or shorter.

By doping a specific host material used in the invention in the lightemitting layer with the phosphorescent material (phosphorescent dopant)having a maximum emission wavelength within the above rages, ahigh-efficiency organic EL device can be obtained.

Reducing Dopant

The organic EL device of the present invention preferably comprises areducing dopant at an interfacial region between the cathode and theorganic thin film layer.

With such a construction, the organic EL device has an improvedluminance and an elongated lifetime.

Examples of the reducing dopant include at least one compound selectedfrom alkali metal, alkali metal complex, alkali metal compound, alkalineearth metal, alkaline earth metal complex, alkaline earth metalcompound, rare earth metal, rare earth metal complex, and rare earthmetal compound.

Examples of the alkali metal include Na (work function: 2.36 eV), K(work function: 2.28 eV), Rb (work function: 2.16 eV), and Cs (workfunction: 1.95 eV), with those having a work function of 2.9 eV or lessbeing particularly preferred. Of the above, preferred are K, Rb, and Cs,more preferred are Rb and Cs, and most preferred is Cs.

Examples of the alkaline earth metal include Ca (work function: 2.9 eV),Sr (work function: 2.0 to 2.5 eV), and Ba (work function: 2.52 eV), withthose having a work function of 2.9 eV or less being particularlypreferred.

Examples of the rare earth metal include Sc, Y, Ce, Tb, and Yb, withthose having a work function of 2.9 eV or less being particularlypreferred.

The preferred metals described above have a particularly high reducingability. Therefore, the emission luminance and life time of an organicEL device can be improved by adding a relatively small amount of themetal to an electron injecting region.

Examples of the alkali metal compound include alkali oxide, such asLi₂O, Cs₂O, K₂O, and alkali halide, such as LiF, NaF, CsF, and KF, withLiF, Li₂O, and NaF being preferred.

Examples of the alkaline earth metal compound include BaO, SrO, CaO, andmixture thereof, such as Ba_(x)Sr_(1-x)O (0<x<1) and Ba_(x)CA¹ _(-x)O(0<x<1), with BaO, SrO, and CaO being preferred.

Examples of the rare earth metal compound include YbF₃, ScF₃, ScO₃,Y₂O₃, Ce₂O₃, GdF₃, and TbF₃, with YbF₃, ScF₃, and TbF₃ being preferred.

Examples of the alkali metal complex, alkaline earth metal complex, andrare earth metal are not particularly limited as long as containing atleast one metal ion selected from alkali metal ions, alkaline earthmetal ions, rare earth metal ions, respectively. The ligand ispreferably, but not limited to, quinolinol, benzoquinolinol, acridinol,phenanthridinol, hydroxyphenyloxazole, hydroxyphenylthiazole,hydroxydiaryloxadiazole, hydroxydiarylthiadiazole,hydroxyphenylpyridine, hydroxyphenylbenzimidazole, hydroxybenzotriazole,hydroxyfulborane, bipyridyl, phenanthroline, phthalocyanine, porphyrin,cyclopentadiene, β-diketones, azomethines, and derivative thereof.

The reducing dopant is added to the interfacial region preferably into aform of layer or island. The reducing dopant is added preferably byco-depositing the reducing dopant with the organic compound (lightemitting material, electron injecting material) for forming theinterfacial region by a resistance heating deposition method, therebydispersing the reducing dopant into the organic material. The disperseconcentration expressed by the molar ratio of the organic material andthe reducing dopant is 100:1 to 1:100 and preferably 5:1 to 1:5.

When the reducing dopant is formed into a form of layer, a lightemitting material or an electron injecting material is made into a layerwhich serves as an organic layer in the interface, and then, thereducing dopant alone is deposited by a resistance heating depositionmethod into a layer having a thickness preferably 0.1 to 15 nm.

When the reducing dopant is formed into a form of island, a lightemitting material or an electron injecting material is made into a formof island which serves as an organic layer in the interface, and then,the reducing dopant alone is deposited by a resistance heatingdeposition method into a form of island having a thickness preferably0.05 to 1 nm.

The molar ratio of the main component and the reducing dopant in theorganic electroluminescence device of the invention is preferably 5:1 to1:5 and more preferably 2:1 to 1:2.

Electron Injecting Layer and Electron Transporting Layer

The electron injecting layer or the electron transporting layer is alayer that aids the injection of electrons into the light emittinglayer, and has a large electron mobility. The electron injecting layeris provided for adjusting an energy level, for example, for reducing anabrupt change in energy level.

It is preferred that the organic EL device of the present inventioncomprises an electron injecting layer between the light emitting layerand the cathode, and the electron injecting layer comprises anitrogen-containing ring derivative as a main component. The electroninjecting layer may function as the electron transporting layer.

The phrase “as a main component” used herein means that the content ofthe nitrogen-containing ring derivative in the electron injecting layeris 50 mass % or more.

An aromatic heterocyclic compound having one or more heteroatoms in amolecule thereof is preferably used as an electron transporting materialused in the electron injecting layer, and a nitrogen-containing ringderivative is particularly preferred. In addition, thenitrogen-containing ring derivative is preferably an aromatic ringcompound having a nitrogen-containing, 6- or 5-membered ring, or a fusedaromatic ring compound having a nitrogen-containing, 6- or 5-memberedring.

The nitrogen-containing ring derivative is preferably, for example, ametal chelate complex of a nitrogen-containing ring represented byformula (A):

wherein each of R² to R⁷ independently represents a hydrogen atom, adeuterium atom, a halogen atom, a hydroxyl group, an amino group, ahydrocarbon group having 1 to 40 carbon atoms, an alkoxy group, anaryloxy group, an alkoxycarbonyl group, or an aromatic heterocyclicgroup, each being optionally substituted.

The halogen atom may include fluorine, chlorine, bromine, and iodine.The substituted amino group may include an alkylamino group, anarylamino group, and an aralkylamino group.

The alkoxycarbonyl group is represented by —COOY′, wherein Y′ isselected from the alkyl groups mentioned above. The alkylamino group andthe aralkylamino group are represented by —NQ¹Q². Examples and preferredexamples of Q¹ and Q² are independently selected from the alkyl groupsand aralkyl groups mentioned above. One of Q¹ and Q² may be a hydrogenatom or a deuterium atom.

The arylamino group is represented by —NAr¹Ar², wherein Ar¹ and Ar² areindependently selected from the non-fused aromatic hydrocarbon groups orthe fused aromatic hydrocarbon groups mentioned above. One of Ar¹ andAr² may be a hydrogen atom or a deuterium atom.

M is aluminum (Al), gallium (Ga), or indium (In), with In beingpreferred.

L in formula (A) is a group represented by formula (A′) or (A″):

wherein each R⁸ to R¹² independently represents a hydrogen atom, adeuterium atom, or a substituted or unsubstituted hydrocarbon grouphaving 1 to 40 carbon atoms. The adjacent two groups may form a ringstructure. Each of R¹³ to R²⁷ independently represents a hydrogen atom,a deuterium atom, or a substituted or unsubstituted hydrocarbon grouphaving 1 to 40 carbon atoms. The adjacent two groups may form a ringstructure.

Examples of the hydrocarbon group having 1 to 40 carbon atoms for R⁸ toR¹² and R¹³ to R²⁷ in formulae (A′) and (A″) are the same as thosedescribed above with respect to R² to R⁷ of formula (A).

Examples of the divalent group formed by the adjacent two groups of R⁸to R¹² and R¹³ to R²⁷ which completes the ring structure includetetramethylene group, pentamethylene group, hexamethylene group,diphenylmethane-2,2′-diyl group, diphenylethane-3,3′-diyl group, anddiphenylpropane-4,4′-diyl group.

The electron transporting compound for the electron injecting layer orthe electron transporting layer is preferably a metal complex including8-hydroxyquinoline or its derivative, an oxadiazole derivative, and anitrogen-containing heterocyclic derivative. Examples of the metalcomplex including 8-hydroxyquinoline or its derivative include a metalchelate oxinoid including a chelated oxine (generally, 8-quinolinol or8-hydroxyquinoline), for example, tris(8-quinolinol)aluminum. Examplesof the oxadiazole derivative are shown below:

wherein each of Ar¹⁷, Ar¹⁸, Ar¹⁹, Ar²¹, Ar²², and Ar²⁵ is a substitutedor unsubstituted aromatic hydrocarbon group or a substituted orunsubstituted fused aromatic hydrocarbon group, and Ar¹⁷ and Ar¹⁸, Ar¹⁹and Ar²¹, and Ar²² and Ar²⁵ may be the same or different. Examples ofthe aromatic hydrocarbon group and the fused aromatic hydrocarbon groupinclude phenyl group, naphthyl group, biphenyl group, anthranyl group,perylenyl group, and pyrenyl group. The optional substituent may be analkyl group having 1 to 10 carbon atoms, an alkoxyl group having 1 to 10carbon atoms or a cyano group.

Each of Ar²⁰, Ar²³, and Ar²⁴ is a substituted or unsubstituted bivalentaromatic hydrocarbon group or a substituted or unsubstituted bivalentfused aromatic hydrocarbon group, and Ar²³ and Ar²⁴ may be the same ordifferent.

Examples of the bivalent aromatic hydrocarbon group or the bivalentfused aromatic hydrocarbon group include phenylene group, naphthylenegroup, biphenylene group, anthranylene group, perylenylene group, andpyrenylene group. The optional substituent may be an alkyl group having1 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms or acyano group.

Electron transporting compounds which have a good thin film-formingproperty are preferably used. Examples of the electron transportingcompound are shown below.

Examples of the nitrogen-containing heterocyclic derivative for use asthe electron transporting compound include a nitrogen-containingheterocyclic derivative having the following formulae but exclusive ofmetal complex, for example, a compound having a 5- or 6-membered ringwhich has the skeleton represented by formula (B) or having thestructure represented by formula (C):

wherein X is a carbon atom or a nitrogen atom and each of Z₁ and Z₂independently represents a group of atoms for completing thenitrogen-containing heteroring.

The nitrogen-containing heterocyclic derivative is more preferably anorganic compound which has a nitrogen-containing aromatic polycyclicring comprising a 5-membered ring or a 6-membered ring. If two or morenitrogen atoms are included, the nitrogen-containing aromatic polycycliccompound preferably has a skeleton of a combination of (B) and (C) or acombination of (B) and (D):

The nitrogen-containing group of the nitrogen-containing aromaticpolycyclic compound is selected, for example, from thenitrogen-containing heterocyclic groups shown below:

wherein R is an aromatic hydrocarbon group or a fused aromatichydrocarbon group each having 6 to 40 carbon atoms, an aromaticheterocyclic group or a fused aromatic heterocyclic group each having 3to 40 carbon atoms, an alkyl group having 1 to 20 carbon atoms, or analkoxy group having 1 to 20 carbon atoms; and n is an integer of 0 to 5.If n is an integer of 2 or more, R groups may be the same or different.

More preferred is a nitrogen-containing heterocyclic derivativerepresented by the following formula:HAr-L¹-Ar¹-Ar²wherein HAr is a substitute or unsubstituted nitrogen-containingheterocyclic group having 3 to 40 carbon atoms; L¹ is a single bond, asubstituted or unsubstituted aromatic hydrocarbon group or fusedaromatic hydrocarbon group each having 6 to 40 carbon atoms, or asubstituted or unsubstituted aromatic heterocyclic group or fusedaromatic heterocyclic group each having 3 to 40 carbon atoms; Ar¹ is asubstitute or unsubstituted divalent aromatic hydrocarbon group having 6to 40 carbon atoms; and Ar² is a substitute or unsubstituted aromatichydrocarbon group or fused aromatic hydrocarbon group each having 6 to40 carbon atoms or a substituted or unsubstituted aromatic heterocyclicgroup or fused aromatic heterocyclic group each having 3 to 40 carbonatoms.

HAr is selected, for example, from the following groups:

L¹ is selected, for example, from the following groups:

Ar¹ is selected, for example, from the following arylanthranyl groups:

wherein R¹ to R¹⁴ are each independently a hydrogen atom, a deuteriumatom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, analkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to40 carbon atoms, a substituted or unsubstituted aromatic hydrocarbongroup or fused aromatic hydrocarbon group each having 6 to 40 carbonatoms, or a substituted or unsubstituted aromatic heterocyclic group orfused aromatic heterocyclic group each having 3 to 40 carbon atoms; andAra is a substituted or unsubstituted aromatic hydrocarbon group orfused aromatic hydrocarbon group each having 6 to 40 carbon atoms or asubstituted or unsubstituted aromatic heterocyclic group or fusedaromatic heterocyclic group each having 3 to 40 carbon atoms.

R¹ to R⁸ may be all selected from a hydrogen atom and a deuterium atom.

Ar² is selected, for example, from the following groups:

In addition, the following compound (refer to JP 9-3448A) is preferablyused as the nitrogen-containing aromatic polycyclic compound for use asthe electron transporting compound:

wherein R₁ to R₄ each independently represent a hydrogen atom, adeuterium atom, a substituted or unsubstituted aliphatic group, asubstituted or unsubstituted alicyclic group, a substituted orunsubstituted aromatic hydrocarbon group, or a substituted orunsubstituted heterocyclic group; and X₁ and X₂ each independentlyrepresent an oxygen atom, a sulfur atom, or dicyanomethylene group.

Further, the following compound (refer to JP 2000-173774A) is alsosuitable as the electron transporting compound:

wherein R¹, R², R³, and R⁴ may be the same or different and eachrepresents an aromatic hydrocarbon group or a fused aromatic hydrocarbongroup each represented by the following formula:

wherein R⁵, R⁶, R⁷, R⁸, and R⁹ may be the same or different and eachrepresents a hydrogen atom or a deuterium atom, and at least one of R⁵,R⁶, R⁷, R⁸, and R⁹ represents a saturated or unsaturated alkoxyl group,alkyl group, amino group, or alkylamino group.

Further, a polymer having the nitrogen-containing heterocyclic group orthe nitrogen-containing heterocyclic derivative is also usable as theelectron transporting compound.

The electron transporting layer preferably comprises at least onecompound selected from the nitrogen-containing heterocyclic derivativesrepresented by formulae (201) to (203):

wherein R is a hydrogen atom, a heavy hydrogen atom, a substituted orunsubstituted aromatic hydrocarbon group or fused aromatic hydrocarbongroup having 6 to 60 carbon atoms, a substituted or unsubstitutedpyridyl group, a substituted or unsubstituted quinolyl group, asubstituted or unsubstituted alkyl group having 1 to 20 carbon atoms, ora substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms;

n is an integer of 0 to 4;

R¹ is a substituted or unsubstituted aromatic hydrocarbon group or fusedaromatic hydrocarbon group having 6 to 60 carbon atoms, a substituted orunsubstituted pyridyl group, a substituted or unsubstituted quinolylgroup, a substituted or unsubstituted alkyl group having 1 to 20 carbonatoms, or an alkoxy group having 1 to 20 carbon atoms;

R² and R³ are each independently a hydrogen atom, a heavy hydrogen atom,a substituted or unsubstituted aromatic hydrocarbon group or fusedaromatic hydrocarbon group having 6 to 60 carbon atoms, a substituted orunsubstituted pyridyl group, a substituted or unsubstituted quinolylgroup, a substituted or unsubstituted alkyl group having 1 to 20 carbonatoms, or a substituted or unsubstituted alkoxy group having 1 to 20carbon atoms;

L is a substituted or unsubstituted aromatic hydrocarbon group or fusedaromatic hydrocarbon group having 6 to 60 carbon atoms, a substituted orunsubstituted pyridinylene group, a substituted or unsubstitutedquinolinylene group, or a substituted or unsubstituted fluorenylenegroup;

Ar¹ is a substituted or unsubstituted aromatic hydrocarbon group orfused aromatic hydrocarbon group having 6 to 60 carbon atoms, asubstituted or unsubstituted pyridinylene group, or a substituted orunsubstituted quinolinylene group;

Ar² is a substituted or unsubstituted aromatic hydrocarbon group orfused aromatic hydrocarbon group having 6 to 60 carbon atoms, asubstituted or unsubstituted pyridyl group, a substituted orunsubstituted quinolyl group, a substituted or unsubstituted alkyl grouphaving 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy grouphaving 1 to 20 carbon atoms; and

Ar³ is a substituted or unsubstituted aromatic hydrocarbon group orfused aromatic hydrocarbon group having 6 to 60 carbon atoms, asubstituted or unsubstituted pyridyl group, a substituted orunsubstituted quinolyl group, a substituted or unsubstituted alkyl grouphaving 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy grouphaving 1 to 20 carbon atoms, or a group represented by —Ar¹—Ar² whereinAr¹ and Ar² are as defined above.

In formulae (201) to (203), R is hydrogen atom, a heavy hydrogen atom, asubstituted or unsubstituted aromatic hydrocarbon group or fusedaromatic hydrocarbon group having 6 to 60 carbon atoms, a substituted orunsubstituted pyridyl group, a substituted or unsubstituted quinolylgroup, a substituted or unsubstituted alkyl group having 1 to 20 carbonatoms, or a substituted or unsubstituted alkoxy group having 1 to 20carbon atoms.

The thickness of the electron injecting layer and the electrontransporting layer is preferably, but not particularly limited to, 1 to100 nm.

It is preferred that the electron injecting layer comprises an inorganiccompound, such as an insulating material and a semiconductor, inaddition to the nitrogen-containing ring derivative. The electroninjecting layer containing the insulating material or the semiconductoreffectively prevents the leak of electric current to enhance theelectron injecting properties.

The insulating material is preferably at least one metal compoundselected from the group consisting of alkali metal chalcogenides,alkaline earth metal chalcogenides, alkali metal halides and alkalineearth metal halides. The alkali metal chalcogenide, etc. mentioned aboveare preferred because the electron injecting properties of the electroninjecting layer are further enhanced. Examples of preferred alkali metalchalcogenide include Li₂O, K₂O, Na₂S, Na₂Se and Na₂O, and examples ofpreferred alkaline earth metal chalcogenide include CaO, BaO, SrO, BeO,BaS and CaSe. Examples of preferred alkali metal halide include LiF,NaF, KF, LiCl, KCl and NaCl. Examples of the alkaline earth metal halideinclude fluorides, such as CaF₂, BaF₂, SrF₂, MgF₂ and BeF₂, and halidesother than fluorides.

Examples of the semiconductor include oxides, nitrides or oxynitrides ofat least one element selected from the group consisting of Ba, Ca, Sr,Yb, Al, Ga, In, Li, Na, Cd, Mg, Si, Ta, Sb and Zn. The semiconductor maybe used alone or in combination of two or more. The inorganic compoundincluded in the electron injecting layer preferably forms amicrocrystalline or amorphous insulating thin film. If the electroninjecting layer is formed from such an insulating thin film, the pixeldefects, such as dark spots, can be decreased because a more uniformthin film is formed. Examples of such inorganic compound include thealkali metal chalcogenide, the alkaline earth metal chalcogenide, thealkali metal halide and the alkaline earth metal halide.

When using the insulating material or the semiconductor, the thicknessof its layer is preferably about 0.1 to 15 nm. The electron injectinglayer in the invention may contain the reducing dopant mentioned above.

Hole Injecting Layer and Hole Transporting Layer

The hole injecting layer or the hole transporting layer (inclusive of ahole injecting/transporting layer) preferably comprises an aromaticamine compound, for example, an aromatic amine derivative represented byformula (I):

wherein each of Ar¹ to Ar⁴ is a substituted or unsubstituted aromatichydrocarbon group or fused aromatic hydrocarbon group having 6 to 50ring carbon atoms, a substituted or unsubstituted aromatic heteroarylgroup or fused aromatic heteroaryl group having 5 to 50 ring atoms, or agroup wherein the aromatic hydrocarbon group or fused aromatichydrocarbon group is bonded to the aromatic heteroaryl group or fusedaromatic heteroaryl group.

Examples of the compound represented by formula (I) are shown below,although not limited thereto.

An aromatic amine represented by formula (II) is also preferably used toform the hole injecting layer or the hole transporting layer:

wherein Ar¹ to Ar³ are the same as defined with respect to Ar¹ to Ar⁴ offormula (I). Examples of the compound represented by formula (II) areshown below, although not limited thereto.

It should be noted that the present invention is not limited to thosedescribed above and it will be understood that variations andmodifications can be effected within the spirit and scope of theinvention.

For example, the following embodiment is one of preferred modificationsof the invention.

In the present invention, the light emitting layer preferably comprisesa charge injection aid.

When a host material having a wide energy gap is used in the lightemitting layer, the difference between the ionization potential (Ip) ofthe host material and Ip of the hole injecting/transporting layer, etc.becomes large, this making the hole injection into the light emittinglayer difficult to likely to increase the driving voltage for obtaininga sufficient luminance.

By adding a hole injecting/transporting charge injection aid into thelight emitting layer, the hole injection into the light emitting layeris facilitated and the driving voltage can be reduced.

For example, a hole injecting/transporting material generally known canbe use as the charge injection aid.

Examples thereof include a triazole derivative, an oxadiazolederivative, an imidazole derivative, a polyarylalkane derivative, apyrazoline derivative, a pyrazolone derivative, a phenylenediaminederivative, an arylamine derivative, an amino-substituted chalconederivative, an oxazole derivative, a fluorenone derivative, a hydrazonederivative, a stilbene derivative, a silazane derivative, apolysilane-based copolymer, an aniline-based copolymer, and anelectroconductive high-molecular oligomer (particularly, thiopheneoligomer).

In addition to the above hole injecting materials, a porphyrin compound,an aromatic tertiary amine compound, and a styryl amine compound arealso preferably used, with an aromatic tertiary amine compound beingparticularly preferred.

Also usable are a compound having two fused aromatic rings in itsmolecule, for example, 4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl(NPD), and a compound having three triphenylamine units connected instar burst configuration, for example, 4,4′,4″-tris(N-(3-methylphenyl)-N-phenylamino)triphenylamine (MTDATA).

Further, a hexaazatriphenylene derivative is preferably used as the holeinjecting material.

An inorganic compound, such as p-type Si and p-type SiC, is also usableas the hole injecting material.

Each layer of the organic EL device of the invention may be formed byany one of known methods such as a vacuum vapor deposition method and aspin coating method, although not particularly limited. The organicthin-film layer containing the compound represented by formulae (1) to(4) and (1′) in the organic EL device is formed by a known method suchas a vacuum vapor deposition method, a molecular beam epitaxy method(MBE method) and a coating method, for example, a dipping method, a spincoating method, a casting method, a bar coating method and a rollcoating method each using a solution of the compound in a solvent.

The thickness of each organic thin film layer in the organic EL deviceof the invention is not particularly limited and preferably severalnanometers to 1 μm because an excessively small thickness may causedefects such as pin holes and an excessively large thickness may requirea high driving voltage.

EXAMPLES

The present invention will be described in more detail with reference tothe examples and comparative examples. However, it should be noted thatthe scope of the invention is not limited to the following examples.

Synthesis Example 1-1 Synthesis of Compound 1-1

In an argon atmosphere, 3-bromofluoranthene (2.3 g, 8.1 mmol),Intermediate 1-1 (3 g, 7.3 mmol), Pd₂(dba)₃ (0.14 g, 0.15 mmol),P(tBu)₃HBF₄ (0.17 g, 0.6 mmol), sodium t-butoxide (1.1 g, 11 mmol), anddry xylene (30 mL) were charged in a three-necked flask in this order,and the resultant mixture was refluxed under heating for 8 h.

The solid generated by adding water to the reaction liquid wassuccessively washed with hexane and methanol and then purified by silicagel column chromatography, to obtain Compound 1-1 (2.9 g, yield: 65%).

FD-MS analysis: m/e=608 for molecular weight of 608.

Synthesis Example 1-2 Synthesis of Compound 1-2

The procedure of Synthesis Example 1-1 was repeated except for usingIntermediate 1-2 (2.5 g, 8.1 mmol) in place of 3-bromofluoranthene andtoluene (30 mL) in place of xylene, to obtain Compound 1-2 (3.3 g,yield: 71%).

FD-MS analysis: m/e=634 for molecular weight of 634.

Synthesis Example 1-3 Synthesis of Compound 1-3

The procedure of Synthesis Example 1-2 was repeated except for usingIntermediate 1-3 (2.5 g, 8.1 mmol) in place of Intermediate 1-2, toobtain Compound 1-3 (3.7 g, yield: 80%).

FD-MS analysis: m/e=634 for molecular weight of 634.

Synthesis Example 1-4 Synthesis of Compound 1-4

The procedure of Synthesis Example 1-2 was repeated except for usingIntermediate 1-4 (2.89 g, 8.1 mmol) in place of Intermediate 1-2, toobtain Compound 1-4 (3.1 g, yield: 63%).

FD-MS analysis: m/e=684 for molecular weight of 684.

Synthesis Example 1-5 Synthesis of Compound 1-5

In an argon atmosphere, into a mixture of 3-iodobromobenzene (28.3 g,100.0 mmol), fluoranthene-3-boronic acid (25.8 g, 105 mmol), andtetrakis(triphenylphosphine)palladium(0) (2.31 g, 2.00 mmol), toluene(300 mL) and a 2 M aqueous sodium carbonate solution (150 mL) wereadded. The resultant mixture was refluxed under heating for 10 h.

Immediately after the reaction, the reaction liquid was filtered and thewater layer was removed from the filtrate. The organic layer was driedover sodium sulfate and then concentrated. The residue was purified bysilica gel column chromatography to obtain Intermediate 1-5 (31.8 g,yield: 89%).

FD-MS analysis: m/e=356 for molecular weight of 356.

Then, the procedure of Synthesis Example 1-2 was repeated except forusing Intermediate 1-5 (2.9 g, 8.1 mmol) in place of Intermediate 1-2,to obtain Compound 1-5 (2.8 g, yield: 56%).

FD-MS analysis: m/e=684 for molecular weight of 684.

Synthesis Example 1-6 Compound 1-6

In an argon atmosphere, Intermediate 1-5 (2.9 g, 8.1 mmol), Intermediate1-6 (3 g, 7.3 mmol), Pd₂(dba)₃ (0.14 g, 0.15 mmol), P(tBu)₃HBF₄ (0.17 g,0.6 mmol), sodium t-butoxide (1.1 g, 11 mmol), and dry xylene (30 mL)were charged in a three-necked flask in this order, and the resultantmixture was refluxed under heating for 8 h.

The solid generated by adding water to the reaction liquid wassuccessively washed with hexane and methanol and then purified by silicagel column chromatography, to obtain Compound 1-6 (3.6 g, yield: 73%).

FD-MS analysis: m/e=684 for molecular weight of 684.

Synthesis Example 1-7 Compound 1-7

The procedure of synthesizing Intermediate 1-5 was repeated except forusing triphenylene-2-boronic acid (28.6 g, 105 mmol) in place offluoranthene-3-boronic acid, to obtain Intermediate 1-7 (30.6 g, yield:80%).

Then, the procedure of Synthesis Example 1-6 was repeated except forusing Intermediate 1-7 (3.1 g, 8.1 mmol) in place of Intermediate 1-5,to obtain Compound 1-7 (4.4 g, yield: 85%).

FD-MS analysis: m/e=710 for molecular weight of 710.

Synthesis Example 1-8 Compound 1-8

The procedure of synthesizing Intermediate 1-5 was repeated except forusing phenanthrene-9-boronic acid (23.3 g, 105 mmol) in place offluoranthene-3-boronic acid, to obtain Intermediate 1-8 (28 g, yield:84%).

Then, The procedure of Synthesis Example 1-6 was repeated except forusing Intermediate 1-8 (2.7 g, 8.1 mmol) in place of Intermediate 1-5,to obtain Compound 1-8 (3.7 g, yield: 77%).

FD-MS analysis: m/e=660 for molecular weight of 660.

Synthesis Example 1-9 Compound 1-9

The procedure of Synthesis Example 1-1 was repeated except for usingIntermediate 1-6 (3 g, 7.3 mmol) in place of Intermediate 1-1, to obtainCompound 1-9 (3.2 g, yield: 72%).

FD-MS analysis: m/e=608 for molecular weight of 608.

Synthesis Example 1-10 Compound 1-10

The procedure of Synthesis Example 1-3 was repeated except for usingIntermediate 1-6 (3 g, 7.3 mmol) in place of Intermediate 1-1, to obtainCompound 1-10 (3.0 g, yield: 65%).

FD-MS analysis: m/e=634 for molecular weight of 634.

Synthesis Example 1-11 Compound 1-11

The procedure of Synthesis Example 1-6 was repeated except for usingIntermediate 1-9 (3 g, 7.3 mmol) in place of Intermediate 1-6, to obtainCompound 1-11 (3.1 g, yield: 62%).

FD-MS analysis: m/e=684 for molecular weight of 684.

Synthesis Example 1-12 Compound 1-12

The procedure of Synthesis Example 1-7 was repeated except for usingIntermediate 1-9 (3 g, 7.3 mmol) in place of Intermediate 1-6, to obtainCompound 1-12 (3.5 g, yield: 68%).

FD-MS analysis: m/e=710 for molecular weight of 710.

Synthesis Example 1-13 Compound 1-13

The procedure of Synthesis Example 1-1 was repeated except for usingIntermediate 1-10 (3 g, 7.3 mmol) in place of Intermediate 1-1, toobtain Compound 1-13 (2.9 g, yield: 65%).

FD-MS analysis: m/e=608 for molecular weight of 608.

Synthesis Example 1-14 Compound 1-14

The procedure of Synthesis Example 1-13 was repeated except for usingIntermediate 1-8 (2.7 g, 8.1 mmol) in place of 3-bromofluoranthene, toobtain Compound 1-14 (3.6 g, yield: 75%)

FD-MS analysis: m/e=660 for molecular weight of 660.

Synthesis Example 1-15 Compound 1-15

In an argon atmosphere, a solution of 3-bromofluoranthene (28.1 g, 100mmol) in THF (1 L) was cooled to −20° C. and then added with a 1.6 Mhexane solution of butyl lithium (69 mL, 110 mmol) dropwise. After 30min, a solution of iodine (28 g, 110 mmol) in THF (500 mL) was added,the temperature was raised to room temperature, and then the solutionwas stirred for 3 h. After adding water to the reaction liquid, theorganic layer was separated and the solvent was evaporated off. Theobtained residue was purified by silica gel column chromatography, toobtain Intermediate 1-11 (23 g, yield: 70%).

Then, into a solution of copper iodide (5.8 g, 30 mmol) indimethylformamide (300 mL), trans-1,2-cyclohexanediamine (6.9 g, 61mmol) was added and then 3-bromocarbazole (15 g, 61 mmol), Intermediate1-11 (20 g, 61 mmol), and tripotassium phosphate (39 g, 183 mmol) werefurther added. The resultant mixture was stirred at 70° C. for 8 h. Thereaction liquid was filtered and the filtrate was concentrated. Theobtained residue was purified by silica gel column chromatography, toobtain Intermediate 1-12 (14.9 g, yield: 55%).

Then, a solution of Intermediate 1-12 (14 g, 31 mmol) in THF (500 mL)was cooled to 20° C. and then added with a 1.6 M hexane solution ofbutyl lithium (23 mL, 37 mmol) dropwise. After stirring for 2 h, asolution of triisopropyl borate (11.7 g, 62 mmol) in THF (50 mL) wasadded dropwise and the resultant mixture was stirred at room temperaturefor 6 h. After adding a 2 N hydrochloric acid, the reaction liquid wasstirred for 30 min and then the organic layer was separated. The solventwas evaporated off and the obtained residue was purified by silica gelcolumn chromatography, to obtain Intermediate 1-13 (7.9 g, yield: 62%).

Then, Intermediate 1-13 (7 g, 17 mmol), 2-bromocarbazole (4.2 g, 17mmol), tetrakis(triphenylphosphine)palladium (0.4 g, 0.3 mmol), toluene(25 mL), dimethoxyethane (25 mL), a 2 M aqueous sodium carbonatesolution (25 mL) were mixed in this order. The resultant mixture wasstirred at 80° C. for 8 h under heating. The organic layer was separatedfrom the reaction liquid and the solvent was evaporated off. Theobtained residue was purified by silica gel column chromatography, toobtain Intermediate 1-14 (4.8 g, yield: 53%).

In an argon atmosphere, Intermediate 1-15 (2.5 g, 8.1 mmol),Intermediate 1-16 (3.9 g, 7.3 mmol), Pd₂(dba)₃ (0.14 g, 0.15 mmol),P(tBu)₃HBF₄ (0.17 g, 0.6 mmol), sodium t-butoxide (1.1 g, 11 mmol), anddry xylene (30 mL) were mixed in this order. The resultant mixture wasrefluxed for 8 h under heating.

The solid generated by adding water to the reaction liquid wassuccessively washed with hexane and methanol. The obtained solid waspurified by silica gel column chromatography, to obtain Compound 1-15(4.0 g, yield: 72%).

FD-MS analysis: m/e=763 for molecular weight of 763.

Example 1-1 Production of Organic EL Device

A glass substrate with an ITO transparent electrode having a size of 25mm×75 mm long×1.1 mm thick (manufactured by GEOMATEC Co., Ltd.) wasultrasonically cleaned in isopropyl alcohol for 5 min and then UV/ozonecleaned for 30 min.

The cleaned glass substrate with the transparent electrode line wasmounted on the substrate holder of a vacuum deposition apparatus. First,the following electron-accepting compound C-1 was vapor-deposited ontothe surface on the side where the transparent electrode line was formedso as to cover the transparent electrode, thereby forming a C-1 filmhaving a thickness of 5 nm. On the C-1 film, the following aromaticamine derivative X1 was vapor-deposited to form a first holetransporting layer having a thickness of 50 nm. Successively after theformation of the first hole transporting layer, the following aromaticamine derivative X2 was vapor-deposited to form a second holetransporting layer having a thickness of 60 nm.

Then, Compound 1-1 obtained in Synthesis Example 1-1 was vapor-depositedon the second hole transporting layer to form a light emitting layerhaving a thickness of 45 nm. At the same time, the following compound D3as a phosphorescent emitting material was co-deposited. Theconcentration of the compound D3 was 8.0% by mass. The co-deposited filmfunctions as a light emitting layer.

Successively after the formation of the light emitting layer, thecompound ET2 was formed into a film having a thickness of 30 nm. The ET2film functions as an electron transporting layer.

Next, LiF was formed into a film having a thickness of 1 nm at a filmforming rate of 0.1 Å/min to form an electron injecting electrode(cathode). On the LiF film, metal Al was vapor-deposited to form a metalcathode having a thickness of 80 nm. Thus, an organic EL device wasproduced.

The obtained organic EL device was measured for the emission efficiencywhile driving the device by constant DC at room temperature at aninitial luminance of 2000 cd/m². The result is shown in Table 1. Thehalf lifetime of the emission was measured while driving the device byconstant DC at room temperature at an initial luminance of 5000 cd/m².The result is also shown in Table 1.

Examples 1-2 to 1-15 and Comparative Examples 1-1 to 1-3

Each organic EL device was produced in the same manner as in Example 1-1except for forming the light emitting layer from the compound listed inTable 1 in place of Compound 1-1. The measured results of the emissionefficiency and the half lifetime are shown in Table 1.

TABLE 1 Emission Half lifetime Voltage efficiency of luminance Hostmaterial (V) (cd/A) (h) Examples 1-1 compound 1-1 4.1 11 550 1-2compound 1-2 4.3 10 450 1-3 compound 1-3 4.2 12 440 1-4 compound 1-4 4.412 400 1-5 compound 1-5 4.3 11 600 1-6 compound 1-6 4.2 12 500 1-7compound 1-7 4.4 10 600 1-8 compound 1-8 4.3 11 560 1-9 compound 1-9 4.112 500 1-10 compound 1-10 4.3 11 600 1-11 compound 1-11 4.0 12 580 1-12compound 1-12 4.3 11 600 1-13 compound 1-13 4.2 13 490 1-14 compound1-14 4.3 10 600 1-15 compound 1-15 4.0 12 600 Comparative Examples 1-1compound 1-A 5.1 9 100 1-2 compound 1-B 5.6 6.5 220 1-3 compound 1-C 5.48.7 180

Comparative Example 1-4

An organic EL device was produced in the same manner as in Example 1-1except for forming the light emitting layer from Compound 1-D in placeof Compound 1-1. No emission from the phosphorescent emitting material(Compound D3) was observed in the obtained organic EL device.

Compounds 1-A and 1-B are disclosed in Patent Document 9, and Compounds1-C and 1-D are disclosed in Patent Document 7.

In the devices using Compounds 1-A and 1-C, the light emitting layercontains excess holes, failing to balance electrons and holes. In thedevice using Compound 1-C, the problem of excess holes cannot becompletely solved, because the electron transporting ability of Compound1-C is poor as compared with that of the biscarbazole derivative of theinvention.

From the above results, it would appear that the compounds of theinvention are superior to the comparative compounds in the emissionefficiency and the lifetime. Namely, the above results show that thespecific fused ring bonded to the biscarbazole derivative is importantfor improving the performance of a host material, and that the aromaticfused ring selected from a fluoranthene, a benzophenanthrene, etc. issuitable as such a fused ring.

Synthesis Example 2-1 Synthesis of Compound 2-1

In an argon atmosphere, 2-bromo-9,9-dimethylfluorene (2.2 g, 8.1 mmol),Intermediate 2-1 (3 g, 7.3 mmol), Pd₂(dba)₃ (0.14 g, 0.15 mmol),P(tBu)₃HBF₄ (0.17 g, 0.6 mmol), sodium t-butoxide (1.1 g, 11 mmol), anddry toluene (30 mL) were charged in a three-necked flask in this order.The resultant mixture was refluxed for 8 h under heating.

The solid generated by adding water to the reaction liquid wassuccessively washed with hexane and methanol and then purified by silicagel column chromatography, to obtain Compound 2-1 (2.7 g, yield: 62%).

FD-MS analysis: m/e=600 for molecular weight of 600.

Synthesis Example 2-2 Synthesis of Compound 2-2

In an argon atmosphere, 2-bromo-9,9-dimethylfluorene (4.4 g, 16.2 mmol),Intermediate 2-2 (3 g, 7.3 mmol), Pd₂(dba)₃ (0.28 g, 0.3 mmol),P(tBu)₃HBF₄ (0.34 g, 1.2 mmol), sodium t-butoxide (2.2 g, 22 mmol), anddry toluene (30 mL) were charged in a three-necked flask in this order.The resultant mixture was refluxed for 8 h under heating.

The solid generated by adding water to the reaction liquid wassuccessively washed with hexane and methanol and then purified by silicagel column chromatography, to obtain Compound 2-2 (3.7 g, yield: 70%).

FD-MS analysis: m/e=716 for molecular weight of 716.

Synthesis Example 2-3 Synthesis of Compound 2-3

In an argon atmosphere, 2-iodophenanthrene (2.46 g, 8.1 mmol),Intermediate 2-1 (3 g, 7.3 mmol), Pd₂(dba)₃ (0.14 g, 0.15 mmol),P(tBu)₃HBF₄ (0.17 g, 0.6 mmol), sodium t-butoxide (1.1 g, 11 mmol), anddry toluene (30 mL) were charged in a three-necked flask in this order.The resultant mixture was refluxed for 8 h under heating.

The solid generated by adding water to the reaction liquid wassuccessively washed with hexane and methanol and then purified by silicagel column chromatography, to obtain Compound 2-3 (3.15 g, yield: 74%).

FD-MS analysis: m/e=584 for molecular weight of 584.

Synthesis Example 2-4 Synthesis of Compound 2-4

In an argon atmosphere, 3-bromofluoranthene (2.3 g, 8.1 mmol),Intermediate 2-1 (3 g, 7.3 mmol), Pd₂(dba)₃ (0.14 g, 0.15 mmol),P(tBu)₃HBF₄ (0.17 g, 0.6 mmol), sodium t-butoxide (1.1 g, 11 mmol), anddry xylene (30 mL) were charged in a three-necked flask in this order.The resultant mixture was refluxed for 8 h under heating.

The solid generated by adding water to the reaction liquid wassuccessively washed with hexane and methanol and then purified by silicagel column chromatography, to obtain Compound 2-4 (2.9 g, yield: 65%).

FD-MS analysis:

m/e=608 for molecular weight of 608.

Synthesis Example 2-5 Synthesis of Compound 2-5

The procedure of Synthesis Example 2-1 was repeated except for using3-(fluoranthene-3′-yl)bromobenzene (2.9 g, 8.1 mmol) in place of2-bromo-9,9-dimethylfluorene, to obtain Compound 2-5 (2.8 g, yield:56%).

FD-MS analysis: m/e=684 for molecular weight of 684.

Example 2-1 Production of organic EL device

A glass substrate with an ITO transparent electrode having a size of 25mm×75 mm long×1.1 mm thick (manufactured by GEOMATEC Co., Ltd.) wasultrasonically cleaned in isopropyl alcohol for 5 min and then UV/ozonecleaned for 30 min.

The cleaned glass substrate with the transparent electrode line wasmounted on the substrate holder of a vacuum deposition apparatus. First,the following electron-accepting compound C-1 was vapor-deposited ontothe surface on the side where the transparent electrode line was formedso as to cover the transparent electrode, thereby forming a C-1 filmhaving a thickness of 5 nm. On the C-1 film, the following aromaticamine derivative X1 was vapor-deposited to form a first holetransporting layer having a thickness of 50 nm. Successively after theformation of the first hole transporting layer, the following aromaticamine derivative X2 was vapor-deposited to form a second holetransporting layer having a thickness of 60 nm.

Then, Compound 2-1 obtained in Synthesis Example 2-1 was vapor-depositedon the second hole transporting layer to form a light emitting layerhaving a thickness of 45 nm. At the same time, the following compound D3as a phosphorescent emitting material was co-deposited. Theconcentration of the compound D3 was 8.0% by mass. The co-deposited filmfunctions as a light emitting layer.

Successively after the formation of the light emitting layer, thecompound ET2 was formed into a film having a thickness of 30 nm. The ET2film functions as an electron transporting layer.

Next, LiF was formed into a film having a thickness of 1 nm at a filmforming rate of 0.1 Å/min to form an electron injecting electrode(cathode). On the LiF film, metal Al was vapor-deposited to form a metalcathode having a thickness of 80 nm. Thus, an organic EL device wasproduced.

The obtained organic EL device was measured for the emission efficiencywhile driving the device by constant DC at room temperature at aninitial luminance of 2000 cd/m². The result is shown in Table 2. Thehalf lifetime of the emission was measured while driving the device byconstant DC at room temperature at an initial luminance of 5000 cd/m².The result is also shown in Table 2.

Examples 2-2 to 2-5 and Comparative Examples 2-1 to 2-3

Each organic EL device was produced in the same manner as in Example 2-1except for forming the light emitting layer from the compound listed inTable 2 in place of Compound 2-1.

TABLE 2 Emission Half lifetime Voltage efficiency of luminance Hostmaterial (V) (cd/A) (h) Examples 2-1 compound 2-1 4.1 11 400 2-2compound 2-2 4.0 10 350 2-3 compound 2-3 4.2 12 420 2-4 compound 2-4 4.111 550 2-5 compound 2-5 4.3 11 600 Comparative Examples 2-1 compound 2-A4.1 12 150 2-2 compound 2-B 4.2 12 120 2-3 compound 2-C 4.9 9 280

The organic EL devices of the invention employing the compounds 2-1 to2-5 exhibit good emission efficiencies and good lifetimes. In contrast,the devices employing the compounds 2-A and 2-B which are disclosed inprior art (Patent Document 9) have shorter device lifetimes. This may beattributable to the presence of an amino substituent which is poor inthe electron resistance or the presence of a fluorenyl group wherein itsactive site is not protected. As compared with the devices of theinvention, the device employing the compound 2-C requires a highervoltage and has a low efficiency. Namely, the results show thatsufficient properties cannot be obtained if the group bonded to9-position of carbazole is an amino group, a fluorenyl group, or anaphthyl group, and further show that it is important to select an arylsubstituent or a fused ring in place such groups.

INDUSTRIAL APPLICABILITY

The material for organic EL devices of the invention is useful for theproduction of an organic EL device which has a long lifetime and a highemission efficiency and can be driven at low voltage, thereby reducing apower consumption.

REFERENCE NUMERALS

-   1: Organic electroluminescence device-   2: Substrate-   3: Anode-   4: Cathode-   5: Phosphorescent light emitting layer-   6: Hole injecting/transporting layer-   7: Electron injecting/transporting layer-   10: Organic thin film layer

What is claimed is:
 1. A biscarbazole derivative of formula. (1)

wherein: each of A₁ and A₂ independently represents an unsubstitutedaromatic hydrocarbon group having 6 to 30 ring carbon atoms; each of Y₁to Y₁₆ independently represents C(R) or a nitrogen atom, and each of Rgroups independently represents a hydrogen atom, a substituent, or avalence bonded to a carbazole skeleton; and each of L₁ and L₂independently represents a single bond or an unsubstituted, divalentaromatic hydrocarbon group having 6 to 30 ring carbon atoms, providedthat: at least one of A₁ and A₂ represents an unsubstitutedfluoranthenyl group, an unsubstituted triphenylenyl group, anunsubstituted benzophenanthrenyl group, an unsubstitutedbenzotriphenylenyl group, an unsubstituted dibenzotriphenylenyl group,an unsubstituted chrysenyl group, an unsubstituted benzochrysenyl group,an unsubstituted picenyl group, an unsubstituted benzo[b]fluoranthenylgroup, or an unsubstituted binaphthyl group; and at least one pair of Rgroups on adjacent ring carbon atoms are bonded to each other to form aring structure together with the ring carbon atoms, wherein either eachof Y₂ and Y₃ represents C(R) wherein R groups are bonded to each otherto form a ring structure together with the ring carbon atoms or each ofY₃ and Y₄ represents C(R) wherein R groups are bonded to each other toform a ring structure together with the ring carbon atoms, wherein atleast one of the following conditions are met: L₁A₁ is different fromL₂A₂; Y₁ different from Y₁₆; Y₂ different from Y₁₅; Y₃ different fromY₁₄; Y₄ different from Y₁₃; Y₅ as represented by C(R) or a nitrogenatom, and each of R groups independently represents a hydrogen atom or asubstituent, is different from Y₁₂ represented by C(R) or a nitrogenatom, and each of R groups independently represents a hydrogen atom or asubstituent; Y₆ as represented by C(R) or a nitrogen atom, and each of Rgroups independently represents a hydrogen atom or a substituent, isdifferent from Y₁₁ represented by C(R) or a nitrogen atom, and each of Rgroups independently represents a hydrogen atom or a substituent; Y₇ asrepresented by C(R) or a nitrogen atom, and each of R groupsindependently represents a hydrogen atom or a substituent, is differentfrom Y₁₀ represented by C(R) or a nitrogen atom, and each of R groupsindependently represents a hydrogen atom or a substituent; and Y₈ asrepresented by C(R) or a nitrogen atom, and each of R groupsindependently represents a hydrogen atom or a substituent, is differentfrom Y₉ represented by C(R) or a nitrogen atom, and each of R groupsindependently represents a hydrogen atom or a substituent.
 2. Thebiscarbazole derivative according to claim 1, wherein each of Y₂ and Y₃represents C(R) wherein R groups are bonded to each other to form a ringstructure together with the ring carbon atoms.
 3. The biscarbazolederivative according to claim 1, wherein each of Y₃ and Y₄ representsC(R) wherein R groups are bonded to each other to form a ring structuretogether with the ring carbon atoms.
 4. The biscarbazole derivativeaccording to claim 1, wherein Y₉ to Y₁₆ represent C(R) wherein at leastone of adjacent pairs of R groups are bonded to each other to form aring structure together with the ring carbon atoms.
 5. The biscarbazolederivative according to claim 1, wherein said biscarbazole derivative isrepresented by formula (2), (3), or (4)


6. The biscarbazole derivative according to claim 1, wherein -L₁-A₁ and-L₂-A₂ are different from each other.
 7. The biscarbazole derivativeaccording to claim 1, wherein at least one of L₁ and L₂ represents anunsubstituted, divalent aromatic hydrocarbon group having 6 to 30 ringcarbon atoms.
 8. The biscarbazole derivative according to claim 1,wherein at least one of L₁ and L₂ represents a single bond.
 9. Thebiscarbazole derivative according to claim 1, wherein A₁ represents anunsubstituted fluoranthenyl group, an unsubstituted triphenylenyl group,an unsubstituted benzophenanthrenyl group, an unsubstitutedbenzotriphenylenyl group, an unsubstituted dibenzotriphenylenyl group,an unsubstituted chrysenyl group, an unsubstituted benzochrysenyl group,an unsubstituted picenyl group, an unsubstituted benzo[b]fluoranthenylgroup, or an unsubstituted binaphthyl group; and A₂ represents anunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms.
 10. The biscarbazole derivative according to claim 1, wherein A₁represents an unsubstituted fluoranthenyl group, an unsubstitutedbenzophenanthrenyl group, or an unsubstituted benzotriphenylenyl group.11. The biscarbazole derivative according to claim 1, wherein A₂represents an unsubstituted phenyl group, an unsubstituted biphenylgroup, an unsubstituted terphenyl group.
 12. The biscarbazole derivativeaccording to claim 1, wherein A₁ represents an unsubstitutedfluoranthenyl group, an unsubstituted triphenylenyl group, anunsubstituted benzophenanthrenyl group, or an unsubstitutedbenzotriphenylenyl group; A₂ represents an unsubstituted phenyl group,an unsubstituted biphenyl group, or an unsubstituted terphenyl group; atleast one of L₁ and L₂ represents an unsubstituted, divalent phenylgroup, an unsubstituted, divalent naphthyl group, or an unsubstituted,divalent phenanthrenyl group; and Y₁ to Y₁₆ all represent C(R) whereineither of one pair of R groups in Y₂ and Y₃ or one pair of R groups inY₃ and Y₄ are bonded to each other to form a ring structure togetherwith the ring carbon atoms and each of the other R groups independentlyrepresents a hydrogen atom, or a valence bonded to a carbazole skeleton.13. The biscarbazole derivative according to claim 1, wherein A₁represents an unsubstituted fluoranthenyl group, an unsubstitutedtriphenylenyl group, an unsubstituted benzophenanthrenyl group, or anunsubstituted benzotriphenylenyl group; A₂ represents an unsubstitutedphenyl group, an unsubstituted biphenyl group, or an unsubstitutedterphenyl group; L₁ and L₂ represent a single bond; and Y₁ to Y₁₆ allrepresent C(R) wherein either of one pair of R groups in Y₂ and Y₃ orone pair of R groups in Y₃ and Y₄ are bonded to each other to form aring structure together with the ring carbon atoms and each of the otherR groups independently represents a hydrogen atom, or a valence bondedto a carbazole skeleton.
 14. The biscarbazole derivative according toclaim 1, wherein the ring structure represents a benzene ring.
 15. Thebiscarbazole derivative according to claim 1, wherein the biscarbazolederivative is a compound selected from the group consisting of:


16. A biscarbazole derivative represented by formula (1a)

wherein: one of A_(1a) and A_(2a) represents a group represented byformula (a) and the other of A_(1a) and A_(2a) represents anunsubstituted fluoranthenyl group, an unsubstituted benzophenanthrenylgroup, an unsubstituted picenyl group, an unsubstitutedbenzo[b]fluoranthenyl group, or an unsubstituted binaphthyl group; eachof Y_(1a) to Y_(16a) independently represents C(R) or a nitrogen atom,and each of R groups independently represents a hydrogen atom, asubstituent, or a valence bonded to a carbazole skeleton; each of L_(1a)and L_(2a) independently represents a single bond or an unsubstituted,divalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms;and at least one pair of R groups on adjacent ring carbon atoms arebonded to each other to form a ring structure together with the ringcarbon atoms:

wherein Y₂₁ represents a nitrogen atom, each of Y₂₂ to Y₂₅ independentlyrepresents C(R_(a)) or a nitrogen atom, and each of R_(a) groupsindependently represents a hydrogen atom or a substituent.
 17. Amaterial for an organic electroluminescence device, comprising: thebiscarbazole derivative according to claim
 1. 18. An organicelectroluminescence device, comprising: a plurality of organic thin-filmlayers between a cathode and an anode, wherein the plurality of organicthin-film layers comprise a light emitting layer and at least one layerof the organic thin-film layers comprises the biscarbazole derivativeaccording to claim
 1. 19. An organic electroluminescence device,comprising: a plurality of organic thin-film layers between a cathodeand an anode, wherein the plurality of organic thin-film layers comprisea light emitting layer and at least one layer of the organic thin-filmlayers comprises a biscarbazole derivative represented by formula (10):

wherein: one of A₁′ and A₂′ represents an unsubstituted fluorenyl groupand the other of A₁′ and A₂′ represents an unsubstituted aromatichydrocarbon group having 6 to 30 ring carbon atoms; each of Y₁′ to Y₁₆′independently represents C(R′) or a nitrogen atom, and each of R′ groupsindependently represents a hydrogen atom, a substituent, or a valencebonded to a carbazole skeleton; and each of L₁′ and L₂′ independentlyrepresents a single bond or an unsubstituted, divalent aromatichydrocarbon group having 6 to 30 ring carbon atom; and at least one pairof R groups on adjacent ring carbon atoms are bonded to each other toform a ring structure together with the ring carbon atoms, wherein atleast one of the following conditions are met: L₁′A₁′ is different fromL₂′A₂′; Y₁′ different from Y₁₆′; Y₂′ different from Y₁₅′; Y₃′ differentfrom Y₁₄′; Y₄′ different from Y₁₃′; Y₅′ as represented by C(R′) or anitrogen atom, and each of R′ groups independently represents a hydrogenatom or a substituent, is different from Y₁₂′ represented by C(R′) or anitrogen atom, and each of R′ groups independently represents a hydrogenatom or a substituent; Y₆′ as represented by C(R′) or a nitrogen atom,and each of R′ groups independently represents a hydrogen atom or asubstituent, is different from Y₁₁′ represented by C(R′) or a nitrogenatom, and each of R′ groups independently represents a hydrogen atom ora substituent; Y₇′ as represented by C(R′) or a nitrogen atom, and eachof R′ groups independently represents a hydrogen atom or a substituent,is different from Y₁₀′ represented by C(R′) or a nitrogen atom, and eachof R′ groups independently represents a hydrogen atom or a substituent;and Y₈′ as represented by C(R′) or a nitrogen atom, and each of R′groups independently represents a hydrogen atom or a substituent, isdifferent from Y₉′ represented by C(R′) or a nitrogen atom, and each ofR′ groups independently represents a hydrogen atom or a substituent. 20.The organic electroluminescence device according to claim 18, whereinthe light emitting layer comprises the biscarbazole derivative as a hostmaterial.
 21. The organic electroluminescence device according to claim20, wherein the light emitting layer comprises a phosphorescentmaterial.
 22. The organic electroluminescence device according to claim21, wherein the light emitting layer comprises the host material and thephosphorescent material which is an ortho-metallated complex of a metalatom selected from the group consisting of iridium (Ir), osmium (Os),and platinum (Pt).
 23. An organic electroluminescence device accordingto claim 22, further comprising: an electron injecting layer between thecathode and the light emitting layer, wherein the electron injectinglayer comprises a nitrogen-containing ring derivative.
 24. The organicelectroluminescence device according to claim 23, further comprising: anelectron transporting layer between the cathode and the light emittinglayer, wherein the electron transporting layer comprises thebiscarbazole derivative.
 25. The organic electroluminescence deviceaccording to claim 24, further comprising: a hole transporting layerbetween the anode and the light emitting layer, wherein the holetransporting layer comprises the biscarbazole derivative.
 26. A lightingdevice, comprising: the organic electroluminescence device according toclaim
 18. 27. A display device, comprising: the organicelectroluminescence device according to claim 18.